(a) Technical Field
The present disclosure relates to a liquid crystal display.
(b) Discussion of the Related Art
A conventional liquid crystal display (LCD) includes two display panels provided with pixel electrodes and a common electrode, and a liquid crystal layer interposed between the two panels and having dielectric anisotropy. The pixel electrodes are arranged in a matrix shape, and are connected to a switching element, such as a thin film transistor (TFT), so as to be sequentially applied with a data voltage row by row. The common electrode is formed on an entire surface of the display panel and is applied with a common voltage. The pixel electrodes, the common electrode, and the liquid crystal layer therebetween form a liquid crystal capacitor an overall circuit, and the liquid crystal capacitor is a basic unit constituent of a pixel along with a switching element connected thereto.
In such a liquid crystal display, voltages are applied to the two electrodes so as to form an electric field in the liquid crystal layer, and transmittance of light passing through the liquid crystal layer is regulated by regulating an amplitude of the electric field so as to obtain a desired image. In order to prevent a degradation phenomenon caused by the application of an electric field in one direction to a liquid crystal layer for a long period of time, the polarity of the data voltage with respect to the common voltage is inverted for respective frames, respective rows, or respective pixels.
Various methods are presently being tried as an effort to improve motion picture display characteristics of such a liquid crystal display, for example, a high speed driving method driving at the speed of 120 frames per second is under development. For high speed driving, a response speed of the liquid crystal should be two times the speed of 60 frames per second, and it is now estimated that this is possible.
In addition, since a large amount of electrical power is consumed as a result of the high frame speed used in the high speed driving technique, an attempt to minimize power consumption has been tried by adopting a column inversion in an inversion driving method.
The column inversion changes the polarity of a data voltage of the same data line by one frame, and since the number of inversions of the data voltage is one in one frame, power consumption characteristics are substantially enhanced.
There are two problems with the column inversion, however. One of the problems is a coupling defect, and the other is a stripe defect.
The coupling defect is a phenomenon that the respective luminances of an upper portion and a lower portion of a liquid crystal panel assembly become different from each other since a data voltage of the same polarity is continuously applied for one frame because of parasitic capacitance generated by an overlap of the data lines and the pixel electrodes. More specifically, a vertical crosstalk phenomenon occurs, where, if a box having a higher gray value than a root image is displayed on the root image having a low gray value, portions above and below the box have different gray values from the root image. In order to solve this coupling problem, a ratio of the parasitic capacitance due to the overlap of the data line and the pixel electrode to an entire capacitance of the device should be less than or equal to 1%, and to achieve this is difficult.
The stripe defect is a phenomenon where a stripe is formed when data voltages of the same polarity are applied in a vertical directions and there is a difference between data voltages of a positive polarity and a negative polarity.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.